Judgment of the Court (First Chamber) of 21 May 2026.#BD v Sociálna poisťovňa, ústredie.#Request for a preliminary ruling from the Najvyšší správny súd Slovenskej republiky.#Reference for a preliminary ruling – Social security – Regulation (EC) No 883/2004 – Coordination of social security systems – Retirement pensions – Article 51(1) – Periods of insurance completed in a specific activity as an employed or self-employed person or in an occupation which is subject to a special scheme – Concept of ‘special scheme’ – Rules for aggregating periods of insurance – National legislation which treats workers coming within certain categories more favourably – Articles 45 and 48 TFEU – Free movement of workers.#Case C-717/24.